LARE Irrigation Design Flashcards

Which formula correctly calculates precipitation rate (PR) in inches per hour for a sprinkler zone?

Answer: PR = (96.25 × GPM) ÷ Area (sq ft)

The precipitation rate formula PR = (96.25 × GPM) ÷ area converts the zone's total flow in gallons per minute to an equivalent depth in inches per hour over the coverage area.

Which backflow preventer assembly provides the highest level of protection and is required for high-hazard irrigation connections?

Answer: Reduced pressure zone assembly (RPZ)

The reduced pressure zone (RPZ) assembly offers the highest protection through two independently acting check valves and a monitored relief valve that opens if either check valve fails.

What does ET₀ (reference evapotranspiration) represent in irrigation science?

Answer: Evapotranspiration from a standardized hypothetical grass reference surface used as a baseline

ET₀ is calculated from a standardized hypothetical grass reference crop and serves as the baseline value from which crop coefficients (Kc) are applied to estimate water demand for any plant type.

Which soil amendment most effectively improves water retention in sandy soils?

Answer: Organic compost

Organic compost improves water retention in sandy soils by increasing organic matter content, which creates water-holding microsites and improves soil aggregation.

What is the primary function of a flow sensor connected to an irrigation controller?

Answer: To detect abnormal flow rates from pipe breaks or stuck valves and signal the controller to shut down the master valve

A flow sensor monitors water flow and alerts the controller when flow is abnormally high (indicating a break) or continuous between cycles (indicating a stuck valve), triggering master valve closure to prevent waste.

Which factor most directly determines the throw radius of a sprinkler head?

Answer: Operating pressure at the head

Operating pressure at the nozzle is the primary determinant of throw radius; heads are engineered for an optimal pressure range, and deviations reduce coverage radius and distribution uniformity.

What is the correct sequence of components from the water meter to the irrigation zone valve in a properly designed system?

Answer: Meter → backflow preventer → master valve → filter → zone valve

The correct sequence is: meter, then backflow preventer (protecting the potable supply), then master valve (system shutoff), then filter (protecting downstream components), then zone valves.